David Rittenhouse was a real person and a rich clock-maker - but his only surviving children were two daughters; he had no son who could have carried on his tradition. The portrayal of his character is a plot device.
Writer Stephen King is related to the real-life David Rittenhouse. His great-grandfather was named David Rittenhouse Pollock, and through David's mother, King is a descendant of David Rittenhouse's brother.
The actor who plays David Rittenhouse is Armin Shimerman, who played Quark in Star Trek: Deep Space Nine (1993). Earlier in this episode, there is a picture on the wall at Jiya's apartment of the Vulcan hand gesture made famous by Spock in Star Trek (1966).
Flynn tells Lucy that when he was younger, he wanted to be a cowboy. In one of his first American roles, Goran Visnjic played an Eastern European cowboy wannabe in Practical Magic (1998).
The letter that Benedict Arnold wrote has what George Washington called a sympathetic stain. The sympathetic stain was used by members of the Culper Spy Ring, which Washington was in charge of, to put sensitive info in letters - and if they were captured, the info would remain secret. Benedict Arnold had been a member of the Culper Spy Ring until news of him becoming a turncoat became known.